Purple loosestrife identification

Before control activities begin, be sure you are correctly identifying purple loosestrife.

Purple loosestrife flower up-close

Flower: Individual flowers have five or six pink-purple petals surrounding small, yellow centers. Each flower spike is made up of many individual flowers.

Purple loosestrife seed capsule and seed

Seed Capsule: As flowers begin to drop off, capsules containing many tiny seeds appear in their place. Depending on where you live, plants may go to seed as early as late July.

Seed: Each mature plant can produce up to 2.7 million seeds annually. As tiny as grains of sand, seeds are easily spread by water, wind, wildlife and humans. Germination can occur the following season, but seeds may lay dormant for several years before sprouting.

Purple loosestrife leaf and stalk

Leaves: Leaves are downy, with smooth edges. They are usually arranged opposite each other in pairs which alternate down the stalk at 90 degree angles, however, they may appear in groups of three.

Stalks: Stalks are square, five or six-sided, woody, as tall as 2 meters (over 6 feet) with several stalks on mature plants.

Purple loosestrife roots

Rootstock: On mature plants, rootstocks are extensive and can send out up to 30 to 50 shoots, creating a dense web which chokes out other plant life.


Don't be fooled by these look-alikes...

Fireweed

Fireweed (Epilobium angustifolium)
Conical flower spike is 10-13 centimeters (4-5 inches) wide at the base. Stem is round and leaves alternate.

Blue Vervain

Blue Vervain (Verbena hastata)
Small purple flower spikes; edges of leaves are toothed.

Swamp Loosestrife

Swamp Loosestrife (Decodon verticillatus)
Individual flowers ring the stem above leaf pairs.

Winged Loosestrife

Winged Loosestrife (Lythrum vigatum)
Leaves alternate with small stems attaching to main stem.